#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=0x3f3f;
int n;
int a[30];
string s[150000000];
string m;
bool c(string a,string b){
	int x=a.length(),y=b.length();
	int minn=min(x,y);
	for(int i=1;i<=minn;i++)
		if(a[i]!=b[i])
			return a>b;
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>s[i];
	sort(s+1,s+n+1,c);
	for(int i=1;i<=n;i++)
		m+=s[i];
	cout<<m;
	return 0;
}